I'm putting a contract together. I had a previous verbal agreement with my client that they pay my invoices within 2 weeks (issued on a weekly basis), but it feels too long. So I want to have a clause in the contract to reflect a shorter period - say 1 week. What is a reasonable amount of time to pay weekly invoice.
I put net 15 days on invoices.
15 days is customarily the minimum. Remember payment may need to be routed through accounting, or the mail if a check is sent. You can't expect or require immediate payment in most cases, even though it's nice when clients do that.
For a weekly invoice, with 15 days you'll always be a week behind. The other option would be to request the first week up front (at contract signing), that way you are always a week ahead and can stop work if payment hasn't been received for the the coming week.
Always make it clear, in writing, what the payment terms and deadlines are. I've seen anything from 10 to 60 days in various industries, but never less than 10 days. As already mentioned, there are a lot of hoops to jump internally for some companies to cut a check, so give them a reasonable amount of time. On the other hand, some companies will put off paying you as long as possible if there are no late penalties (especially if they have cash-flow issues already).
Include a moderate late payment penalty, both in the contract and on each invoice, and hold them to it. Late penalties are fairly standard, and something like 10-20% APY is common - see this article for how to apply the penalties, and send them a new invoice within after the due date that includes the new penalty.
Consider the trade off between your business relationship and prompt payment. If a client is always a few days late, but always pays, is demanding a check 2 days earlier really going to matter if it might cost you the customer? On the flip side, if you're spending hours of your time chasing someone for money after each project, you might be ahead to drop them. Either way, discuss it with them. You might choosing to waive the late penalty for a good client - but make sure they are aware it is a per-instance exception and not a change to your terms (but don't rub their face in it).
In your particular case, where you have already agreed to an invoicing period, even though it was 'only' verbally, I would be very hesitant to try changing that on a written contract. As a client, I would see that as pulling a fast one and would a little be wary of trusting you in the future. If this project goes well, you can always adjust the terms on the next project.
What is reasonable in the circumstances depends on what you feel comfortable working out with the client.
I think the best solution in your scenario is to very politely ask the client if you can shorten the payment terms to 1 week - you've got nothing to lose.
They'll likely prioritize your invoices over their other bills (esp. if and when they are short on cash flow) because you asked.
You have to have a sense of what you can openly discuss and ask of the client without irritating them - but if you feel comfortable go for it.
For over 40 years I have been making hardwood floors for clients all over UK and across the world. I give fixed price quotations for 99% of the work and they rangemin costs from around £5k and £300K. I have always charged 70% of contract value up-front, only occasionally varying that to 50% with confirmation of the clients order and 25% prior to loading for delivery, the 30% or 25% balance being due on the day of completion of the works. I never have any problems with customers paying up-front. Some part with very large sums of money sometimes 2 years ahead of any materials being delivered to site. I also am always paid very promptly. Though the Terms of Trading require payment on the day of completion, in practice it usually takes me a day or two to produce the invoice, which is invariably sent by email. It is very rare that I am not paid the balance within 2 to 3 days of sending the email. I do not work for anyone who wants to pay in arrears. However, to support that, I never let the customer down. I always deliver what the quote says. We strive for perfection on every job. We never have to go back to do put rights. If only more small businesses took the same approach to payment and to the quality of work delivered the courts would be much less busy.