It is very good practice to request payment from others as soon as practically possible.
This doesn’t just apply to services rendered or products sold, but also to settling balances on a personal level.
There will always be a lag between when you request payment and when money is received, and you don’t want to exacerbate this further by forgetting to send the initial request (which is surprisingly easy to do).
Sometimes people aren’t comfortable invoicing right away as they consider it to be pushy, but I assure you this isn’t rude. You’re simply providing the means for payment upfront for the benefit of both parties.
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