The classical Gleason-Kahane-Żelazko Theorem states that a linear functional on a complex Banach algebra not vanishing on units, and such that $$\Lambda (\textbf{1})=1$$
Λ
(
1
)
=
1
, is multiplicative, that is, $$\Lambda (ab)=\Lambda (a)\Lambda (b)$$
Λ
(
a
b
)
=
Λ
(
a
)
Λ
(
b
)
for all $$a,b\in A$$
a
,
b
∈
A
. We study the GKŻ property for associative unital algebras, especially for function algebras. In a GKŻ algebra A over a field of at least 3 elements, and having an ideal of codimension 1, every element is a finite sum of units. A real or complex algebra with just countably many maximal left (right) ideals, is a GKŻ algebra. If A is a commutative algebra, then the localization $$A_{P}$$
A
P
is a GKŻ-algebra for every prime ideal P of A. Hence the GKŻ property is not a local-global property. The class of GKŻ algebras is closed under homomorphic images. If a function algebra $$A\subseteq {\mathbb {F}}^{X}$$
A
⊆
F
X
over a subfield $${\mathbb {F}}$$
F
of $${\mathbb {C}}$$
C
, contains all the bounded functions in $${\mathbb {F}}^{X}$$
F
X
, then each element of A is a sum of two units. If A contains also a discrete function, then A is a GKŻ algebra. We prove that the algebra of periodic distributions, and the unitisation of the algebra of distributions with support in $$(0,\infty )$$
(
0
,
∞
)
satisfy the GKŻ property, while the algebra of compactly supported distributions does not.