Is 賖 just a variant of 賒？ 賒 is clearly defined as “delaying payment for something” in Chinese dictionaries; it commonly appears in the phrase “賒帳”, which has a similar meaning. 

賖 is a Chữ Nôm used to write “xa” in Vietnamese, which means “far”. To me, it seems like 賖 is a corruption of 賒, since 賒 is pronounced like “xa” as far as I know. On the other hand, there is no entry for “賖” in Chinese dictionaries, and might be a Vietnamese innovation. However, that would also be weird since its pronunciation is markedly different than other characters which also have the 余 component.

余- dư
餘- dư

Has 賖 ever been used in Chinese? Is it related to 賒?

EDIT: AFAIK, 賖 is also used for xơ, but this sound also doesn’t come close to the expected pronunciation.
賖 is listed in Hanyu Da Cidian and defined as:


  shē
  同“賒1”。


The entry for 賒 says:


  1 买物延期交款。




Zisea also just notes:


  同【赊】。 


Not sure if their info is from 字海 or 汉语大字典 but there is no mention of Chữ Nôm in either of the references. It seems to just be treated as a variant in modern Chinese.



Wiktionary also gives the following references:


  参考
  - 大字源：1673页，第14字
  - 汉语大字典：第6卷，3643页，第2字
  - 宋本广韵：165页，第3字
  - 辞海：1275页，第5行，第4字
  - Unihan数据：U+8CD6


and only mentions:


  异体字
   赊