Everything is humming with a client’s project—and then suddenly, silence. Your emails get no response. Your phone calls go unreturned. You try a text message. It gets ignored, too.

Should you be worried? Maybe. Maybe not. There are plenty of reasons a client may go dark on you temporarily and most of them usually boil down to being busy.

That said, if you’re reaching out about something that’s time-sensitive, getting the client’s attention may be critical. If you need a client’s okay to move on to the next step on a deadline project, for instance, there’s no substitute for getting a response.

So how do you get the attention you need—without becoming a pest? Use these strategies.

Root out communication snafus.

If you’ve been reaching out to clients who aren’t responding, it’s possible that something is going wrong in the communication process. Maybe your emails are landing in an over-crowded inbox. Or perhaps a client has a new team member  who isn’t as speedy as the last one.

A friendly reminder is often the best first step toward re-establishing contact. For instance, you might forward the original message with a note saying, “Just making sure you saw this.” If you’re checking on payment, you might send a note saying, “Just noticed this invoice was not paid, and 30 days have passed. I’m re-sending in case it got lost in your inbox.”

If you’re worried that your messages are ending up in someone’s spam filter, try cc’ing an alternate email address or sending a text message saying, “Hope all is well! I emailed you with a question on a deliverable on 5.20 and didn’t hear back. I’m going to re-send the message to your inbox now, so we don’t fall behind on the project.”

Set a deadline.

If you’re under the gun, send a note to the client with a respond-by date or time in the subject line. For instance: “Urgent: Printer’s deadline! Please respond by noon on June 2, 2017.” In your note, make sure the client knows why you are hurrying them. You might say, “Sorry for the rush, but we’re out of time. We have to ship the brochure to the printer by 3 pm today. If we don’t hear from you by noon, we’ll assume you are signed off.”

If you take this approach, it is best to CC a couple of other contacts at the firm who are engaged in the project, or the client’s administrative assistant, in case there is a factor you don’t know about. The alternative is to write your contracts so that you address what will happen if the client does not respond in a timely manner, so you are both in agreement.

Give it a week.

If you’re reaching out about a matter that is time-sensitive, but where you have some wiggle room, consider the possibility that clients are not responding because of a vacation, illness, business travel or a major company initiative such as a conference—that might have caused them to fall behind on keeping in touch. If so, pinging them repeatedly isn’t going to help the situation and may just annoy them. If you’ve tried them twice and still get no response, try waiting a week and then re-contacting them with a note saying, “I think you may have been out last week, as I never heard back when I emailed you.”

Be tactful.

If you’ve reached out in a friendly way a couple of times, taken a breather and then reached out again, it is possible there’s a serious problem. Try sending an email with a subject line that says “Hope you are okay!” or leaving a message on the client’s voicemail to that effect. You might say something along the lines of, “I wanted to check in, as I haven’t heard from you about the project in three weeks, and you’re usually very reachable. I’m going to put the project on hold until I hear back from you, in case there’s anything we need to discuss. I hope all is okay for you.”

If you still don’t hear back, try calling the client’s office to make sure he or she is alright. If it turns out the client is having a personal or family emergency, you will need to be patient until it resolves.

On the other hand, they could be avoiding you for other reasons such as unhappiness with a deliverable. In that case, simply ask for transparency and offer to hop on a call to talk through issues. It’s best to be open and communicative when there is a disconnect.

Know when to be firm.

Sometimes, a client may be dodging you because he or she owes you money. While there’s no need to take a harsh tone, you do need to properly follow up on invoices so if you do incur a bad debt, your accountant can factor that into your tax return.

If you have sent an invoice and 30 days have passed, try sending a note to check on it. If you haven’t offered the credit card payment option before to avoid processing fees but it is available through your invoicing software, consider turning it on and re-sending the invoice. Include a note to the client that you’ve made electronic payment options available in case that is more convenient for them. (You can usually offer the ACH option, as well, which typically doesn’t require you to pay processing fees).

If you are the service provider, sometimes it is less awkward to have someone else on your team follow up on late invoices, whether that is your administrative assistant or bookkeeper. Treat your clients the way you would want to be treated if you had a cash flow problem, while still remaining firm.

Your professionalism and reputation are very valuable assets. Every communication you have with your clients, even unresponsive ones, is ultimately an opportunity to enhance them—if you don’t let frustration get the better of you.